Toxicity of glyphosate herbicide on Nile tilapia (Oreochromis Niloticus) juvenile

Most aquatic herbicides have undergone some toxicity testing for effects on non-target aquatic organisms, little of this testing has been conducted on early life stages of Clarias gariepinus. African catfish C. gariepinus were exposed to acute concentrations of glyphosate for 96hrs. The lethal concentration (LC ) 5O value of glyphosate was 0.295 mg l for 96h of exposure. The mean mortality percentages were 0, 0, 43, 73, 93 1 and 96% in the order of concentration of 0, 19, 42, 94, 207 and 455 mg l , respectively. Glyphosate 1 concentration corresponding to the 96h LC value for juvenile C. gariepinus was used to study the effects of 5O glyphosate exposures in inducing histopathological changes of gills, liver, kidney and brain. In the gills, cellular infiltrations were observed. In the liver there was fatty degeneration, severe fat vacuolation, diffuse hepatic necrosis and darkly stained specks of necrotic nuclei and infiltration of leukocytes. In kidney there was haematopoietic necrosis and severe pyknotic nuclei. The brain showed mononuclear infiltration, neuronal degeneration and spongiosis. These changes occurred predominantly in the 96h exposure. Respiratory stress, erratic swimming and death of fish were observed in exposed fish which varies with the concentration of the toxicant and its showed that mortality increased with increasing in concentration. Glyphosate is toxic to juvenile fish. C. gariepinus are more susceptible to herbicide, therefore their use on/near fish farm or in area close to aquatic environment should be discouraged.